Inner tube and method of making the same



July 25, 1944. R. F. WILSON ETAL INNER TUBE AND METHOD OF MAKING THE SAME Filed April 10, 1942 2 Sheets-Sheet l AND WI LLMZP L. KLINGMAH July 25, 1944. R. F. WILSON ET AL INNER TUBE AND METHOD MAKING THE SAME Fild April 10, 1942 2 Sheets-sheet 4205122:- F: wmson HO WILLARD LJGJNGMAN T f abtouwg Patented 25, 1944 INNER TUBE AND MEA'lggD E MAKING THE 8 Robert F. Wilson and Willard L. Kiingman, Akron, Ohio, assignors to The Firestone Tire 8;

Rubber Company, of Ohio Akron, Ohio, a corporation Application April 10, 1942, Serial No. 438,504

'lhlsjnvention relates to inner tubes and to ads 'of manufacturing the same, and more especially itrelates to compartment inner tubes comprising a plurality of circumferentially extending compartments or chambers, and to improved procedure for the manufacture thereof.

The'chief object of the invention is to increase the safety of motor vehicles. More specifically the invention aims to provide an inner tube for Pneumatic tires that cannot lose more than half its internal pressure from any single punctureor blow out; that is so constructed that the pressure in the tube automatically, is equalized throughout the tube after a compartment thereof is defiated through puncture or blowout; that auto- 15 matically seals the puncture or blowout after the ruptured compartment is deflated; and to provide a simple method for the facile manufacture of inner tubes of the character mentioned. Other objects will be manifest.

Of the accompanying drawings:

Figure 1 is a transverse section of a vulcanized annular rubber tube, showing the first steps in the manufacture of the improved inner tube;

Figure 2 is a view of the structure shown in Figure 1 in a succeeding stage of manufacture;

Figure 3 is a fragmentary, sectional, perspective view of a pneumatic tire mounted upon a rim, and the improved inner tube mounted in said tire, the latter showing a blowout on the centerline of its periphery, and showing internal partitions in normal position in full lines, their positions following a blowout being indicated by broken lines:

Figure 4 shows the same elements that are shown in Figure 3, the tire showing a blowout in its periphery, at one side of the centerline thereof;

Figure 5 is a view similar to Figure 1 showing the first steps in the manufacture of a modified embodiment of the invention;

Figure 6 is a view of the structure shown in Figure 5 in a succeeding stage of manufacture;

Figure 7 is a view similar to Figure 3 showing the modified er tube as it appears in a tire casing ha a blowout on the centerline of its periphery, and showing internal partitions in normal position in full lines, their positions oliowing a blowout being indicated by broken lines: and a Referring to the drawings, the first step to provide an annular, Vulcanized rubber tube II, the same being slightly smaller in size than standard inner tubes designed for use in the same size tires. The tube It may be made by any known or preferred method, and in Figure 1 is shown as including a valve stem II that is disposed at an angle to the plane of the tube, although it may be positioned in the plane of the tube if so desired. The tube It is then buffed circumferentially in three separated regions, namely, along the centerline of the periphery of the tube, and along each of the regions that are disposed adjacent the beads of a tire when the tube is mounted therein, said bufied regions being aboutl20" apart transversely of the tube, and being indicated at B, B in Figure l of the drawings.

The next step in the manufacture of the inner tube is the application of suitable adhesive, such as rubber cement, to the buffed regions B of the tube, said adhesive being indicated at l8, it Figure 2. Thereafter an endless band of mmcanized sheet ruber I4 is applied circumferentially and symmetrically to the periphery of the tube ill, the respective lateral margins of the band H- and the medial region thereof being adhered to the tube through the agency of the adhesive l3. Preferably a suitable lubricant is placed between the tube It and band It to prevent adhesion thereof except in those regions where the adhesive I3 is present. The assembled structure is then mounted in a tube mold and subjected to vulcanizing heat while pressure is maintained in the tube It sufficient to force the band It against the mold wall, whereby vulcanization of the band It is effected, and the band is united with the tube It, in the circumferential regions BB, by a vulcanized bond. There are respective small apertures, 15,15, Figures 3 and 4, formed in the wall of the tube It beneath the band It, at each side of the outer peripheral region of adhesion of the band and tube. The apertures II need not be symmetrically disposed. and they may be made by a hot wire that is inserted into the tube through the valve stem I I.

In Figures 3 and 4 the improved inner tube is shown as it appears when mounted for use within a tire casing II, the

latter being mounted upon a drop center tire rim II. when the inner tube is inflated by means of the of the infiowing air passes tive apertures II, with the shown in Figure 4.

of the band ll,iseuuslised and said portionsof tended against the inner surface of the tire easing. Said chordal portions ,are indicated by the numerals ll, II, and they divide the inflated tube into three compartments of which 20 is a central compartment and fl, .II are respective lateral compartments of somewhat smaller size.

The functioning of the improved inner tube in case of puncture or blowout is shown in Figures 3 and 4 of which Figure 3 shows the Lslllt of a blowout on the centerline of the tire tread, said blowout being indicated at 23. The result of said blowout is to rupture the inner tube at the periphery of its central compartment 20, which causes rapid deflation of the latter, but the apertures It in the chordal portions is are so small in size as to prevent substantial escape of air from compartments 2i before the differential pressure in compartments 20, 2| forces said chordal portions into face to face engagement with each other, as indicated in broken lines in Figure 3. When said chordal portions are thus disposed, further escape of air through apertures ii is prevented, and the air in compartments 2|, amounting to about half of the original amount of air in the tube, will provide sufficient support for the vehicle to prevent the latter from going out of control, and will keep the tire on the rim until repair can be made.

The action of the inner tube in cases where a blowout occurs either side of the centerline of the tire tread is shown in Figure 4, the blowout being indicated at 2|. The result of said blowout is to rupture the outer wall of the inner tube and thus to cause rapid deflation of the contiguous compartment ii. The differential fluid pressure in compartment 2| and deflating compartment fl causes the chordal wall it of the latter to distend into face to face engagement with the ruptured. peripheral wall of the tube, with the resultthat aperture II in said chordal wall is closed and further escape or air from th tube is prevented; At the same time the expansion of the air in the remaining compartment 2i causes chordal wall it I thereof initially to assume the distended position original air remains in the inner tube and the usual results of puncture and blowouts are avoided. Eventually the escape of air from remaining compartment II to compartment 2., through aperture i5, will equalize the pressure in the two compartments and enable the distended intervening wall It to resume its normal position as shown in Fig. 3.

The flrst step in the manufacture of the modilied embodiment of the invention shown in Figures 5 to 8 inclusive is to provide an annular vulcanized rubber tube 21, the same being slightly smaller in size than standard inner tubes designed for use in the same size tires. The tube 21 as shown includes a valve stem 28 that extends radially inwardly in the medial plane of the tube. Next the tube 2! is buffed circumferentialiy in three separated regions, namely, along the centerline of the inner circumference of the tube, and along th periphery of the tube at each side of the centerline thereof, approximately in the regions that are coincident with the shoulders of the tread portion of a tire in which the tube ultimately is used. The buifed regions are indicated at B, B in Figure 5 of the drawings.

The next step in the manufacture of the im- Thus more than half of the proved tube is the application of adhesive to the 1s buffed regions 3 or the tube 21, said adhesive being indicated at It, 20, Figure 6. Thereafter an endlessbandofunvuleaniaedsheetrubberllis applied circumferentiallv and symmetrically to the inner circumference of the tube 21, the respective lateral margins of the band and the medial region thereof being ahered to the tube through the agency of the adhesive 2!. Suitable lubricant is placed between the tube 21 and band 3 t prevent adhesion thereof except in the regions where the adhesive I. is present. Thereafter the assembled tube is vulcanized in a mold in the manner previously described, after which respective apertures ll, Ii are formed in the opposite walls of the original tube 21, beneath the band ll.

The modifled embodiment of the invention possesses all the advantages inherent in the preferred embodiment, and functions exactly in the same manner as the latter. As is most clearly shown in Figure 'i, when the modified inner tube is inflated within a tire, it is so distended as to form three circumferential compartments ll, 34 and 34 respectively. of which the shape of the middle compartment 31 differs from the middle compartment 20 of the tube shown in 3 chiefly in having a greater area of its on r periphery exposed to the tire casing.

In an alternative'method of fabricating the structures shown in Figures 2 and o-respectively, the outer annular bands, I and II are first made up as annular rubber tubes and vulcanized, after which a circumferential segment is cut therefrom and the remainder of the tube mounted upon the foundation tube I. or 21. Adhesion of the respective parts is effected with air-curing rubber cement. when this method is used, the apertures, I! or II, in the tubes may be formed before the vulcanized bands are applied, and vulcanization of th assembled tubes is not required. In appearance the tubes made by this method are identical with those shown in Figs. 2 and 8 re spectively so that illustration thereof is not believed to be necessary.

The invention makes for safety of life and property and achieves the other advantages set out in the foregoing statement of objects.

Other modification may be resorted to'without departing from the spirit of the invention or the scope of the appended claims, which are not limited wholly to the specific construction shown or exact procedure described.

What is claimed is:

1. An inner tube for pneumatic tires, said inner tube comprising an annular, tubular, rubber structure, means for inflating the same, an annular, transversely arcuate, elastic band mounted upon the exterior face of said tube circumferentially thereof and locally bonded thereto at its lateral margins and along its centerline, there being a relatively small aperture in said tube between the centerline of the overlying band and each of the lateral margins thereof.

2. An inner tube for pneumatic tireasaid inner tube comprising an annular. tubular, rubber structure, means for inflating the same, an annular, transversely arcuate, elastic band symmetrically mounted upon the periphery of said tube circumferentially thereof and locally bonded thereto at its lateral margins and along its centerline, there being a relatively small aperture in said tube between the centeriine of the overlying band and each of the lateral margins thereof.

3. An inner tube for pneumatic tires, said instructure and subjecting it to heat and pressure i ner tube comprising an annular, tubular rubber structure, means for inflating the same, an annular, transversely arcuate elastic band symmetrically mounted upon the entire inner circumferential region of said tube and locally bonded thereto along its lateral margins and along its centerline, there being a relatively small aperture in said tube between the centerline of the band and each of the lateral margins thereof.

4. The method of making inner tubes for pneumatic tires which comprises providing an annular vulcanized rubber tube having an inflating stem, mounting an endless, transversely arcuate rubber band upon the outer surface of the tube, circumferentially thereof, locally bonding said band to the tube along its respective lateral margins and along its centerline, and forming a relatively small aperture in said tube between the centerline of the overlying band and each of the lateral margins thereof.

5. The method of making inner tubes which comprises providing an annular vulcanized rubber tube having an inflating stem, mounting an endless, transversely arcuate, unvulcanized rubber band upon the outer surface of the tube, circumferentially thereof, locally adhering said band to the tube along its respective margins and along its centerline, confining the assembled to heat and internal zation of the band to eflect vulcanization of the band, and then forming a relatively small aperture in said tube between the'centerline of the overlying band and each of the lateral margins thereof.

6. The method of making inner tubes which comprises providing an annular, vulcanized rubber tube having an inflating stein, locally bufling the outside of said tube circumferentially in three concentric, spaced-apart regions, applying adhesive to said bufl'ed regions, mounting an endless, transversely arcuate, unvulcanized rubber band upon said tube and adhering it thereto along its centerline and respective marginal portions by means of the adhesive on the tube, confining the assembled structure and subjecting it pressure to effect vulcaniand to vulcanize it to the tube, and then forming a relatively small aperture in the tube wall between the centerline of the overlying band and each of the lateral margins thereof while utilizing the inflating stem to give access to the said tube wall.

7. A method as defined in claim 6 in which the apertures in the tube wall are formed by burning.

ROBERT F. WILSON. WILLARD L IQJNGMAN. 

